1. Field of the Invention
The present invention pertains to an apparatus for managing heat generated by an electric circuit, such as in a computer environment or the like. More particularly, the present invention pertains to an apparatus for cooling components on a computer add-in card or the like.
2. Related Art
Electric and electronic circuits, particularly integrated circuit (IC) chips, tend to generate an appreciable amount of heat during operation. If the heat is not sufficiently removed from the ambient area surrounding the IC chip, the electronic circuit therein may not operate properly. There are several available options for cooling electric and electronic circuits. One such method is to provide a fan which creates an air flow over the circuits. The air flow typically has a temperature cooler than the ambient air near the electric circuit which leads to a reduction in temperature.
In a computer environment (e.g., a personal computer or workstation), a fan is typically placed at the front or rear of the computer so that cooler air from outside the chassis of the computer may be brought in to the circuits on the main circuit board (also referred to as a motherboard). In some computer chassis, one or more paths may be provided which draw the air flow from the front or rear of the computer to other areas inside the chassis.
Methods for cooling an electric circuit (e.g., an electronic circuit in an integrated circuit (IC) chip such as Pentium(copyright) processor, manufactured by Intel Corporation, Santa Clara, Calif.) are described in Application Note AP-480 xe2x80x9cPentium(copyright) Processor Thermal Design Guidelines Rev. 2.0,xe2x80x9d November 1995 (see, e.g., Pentium(copyright) and Pentium(copyright) Pro Processors and Related Products, 1996, pp. 2-1337 to 2-1363, a copy of which may be obtained from McGraw-Hill Book Company). These methods include the placement of a heat sink on top of the IC chip and increasing air flow over the processor so that the ambient air (heated by the IC chip) may be removed.
Another device for removing heat from an electric circuit, such as an IC chip, is a heat pipe. A heat pipe typically has a round cross-section including two paths extending the length of the pipe. The heat pipe (e.g., an end of the heat pipe) is placed proximately to a component, such as a processor. Working fluid in the heat pipe (e.g., water) is heated at the component and vaporized. The vapor travels away from the component in a hollow, first path of the heat pipe (this first path typically has a relatively large cross-sectional area). Eventually, the vapor is cooled at another location in the heat pipe. For example, the vapor could be cooled over a heat sink device mentioned above. The vapor condenses to form working fluid and the working fluid travels back to the processor through a second path, sometimes referred to as a wick structure, via capillary action. Thus, the heat pipe continuously circulates working fluid and vapor to remove heat from the processor. Further details on the operation of heat pipes may be found in Handbook of Applied Thermal Design (1989, ed., Eric C. Guyer, pp. 7-50 to 7-58).
Yet another example of a device for reducing heat in a computer system is a fan card. A fan card is a computer add-in card that is inserted into a bus connector slot in the motherboard. The fan card includes one or more fans that typical create an air flow in a direction perpendicular to a surface of the card.
A drawback of the aforementioned techniques for managing heat is that they may not work effectively when there are space restrictions. As an example, the Accelerated Graphics Port (AGP) Interface Specification (Rev. 1.0, Intel Corporation, Jul. 31, 1996) and Peripheral Component Interconnect (PCI) Specification (Rev. 2.1, PCI Special Interest Group, Hillsboro, Oreg., 1995) limit the physical dimensions of add-in cards. Referring to FIG. 1, a motherboard 10 in an exemplary computer system is shown. Motherboard 10 includes three PCI connector slots 11a-c for insertion of cards constructed and operating according to the PCI Specification and an AGP connector slot 12 for insertion of a card, such as a graphics accelerator card, constructed and operating according to the AGP specification. A card placed in the AGP connector slot 12 will be relatively close to a card placed in the PCI connector slot 11a. The AGP and PCI specification limit the thickness of the card placed in AGP connector slot 12 to 0.105 inches on the xe2x80x9cbackxe2x80x9d side (i.e., the side facing away from the PCI connector slot 11a) and 0.580 inches on the xe2x80x9cfrontxe2x80x9d side (i.e., the side facing toward PCI connector slot 11a).
With these thickness limitations, the space between the card in PCI connector slot 11a and AGP connector 12 is very limited, making it difficult to cool electric circuits (such as IC chips) on the AGP card. For example, a standard manner for cooling an IC chip is to mount a heat-sink and a cooling fan onto the surface of the IC chip facing away from the card. The combined thickness of the IC chip, heat-sink and fan may exceed the 0.580 inch maximum for the AGP card. Also, even if the combined thickness of these components is less than 0.580 inches, there may be insufficient space between the fan and the card in PCI slot 11a to allow sufficient air flow away from the IC chip, thus impeding the cooling process.
Though smaller versions of the heat-sink and fan may be provided to cool an IC chip, there are several disadvantages in doing so. First, smaller fans generate more noise than larger fans because they need to spin faster to generate the same amount of air flow. Also, because they operate at faster speeds, smaller fans are less reliable (i.e. smaller fans have shorter life spans).
There are also disadvantages in using a heat pipe to remove heat from an IC chip. In an AGP card, the graphical controller IC chip may reach a temperature of 100xc2x0 C. which is passed to the heat pipe making the heat pipe hot, as well. Other devices near the heat pipe may become damaged, such as ribbon cables in the computer system, which may melt at about 80xc2x0 C. The heat pipe is also particularly heavy and may cause a shock or vibration problem (i.e., when the computer chassis is vibrated, the AGP card coupled to the heat pipe may be dislodged from the AGP connector slot 12).
Accordingly, there is a need for an apparatus that improves the removal of heat from an electric circuit such as an IC chip.
An apparatus to cool an electric circuit according to an embodiment of the present invention includes a fan coupled to a ducting structure. The ducting structure is coupled to the fan and is adapted to generate an air flow in the ducting structure over an electric circuit. The ducting structure is adapted to be coupled to a card (for example, a computer add-in card).